The present invention relates to a cleaning device and method for cleaning air or other compressible fluid filters, and also to a compressible fluid pulse generator useful in such cleaning devices and methods. The invention is particularly useful for cleaning, by back flushing, disc-type filters such as described in U.S. Pat. Nos. 5,797,978; and 4,661,250, the disclosures in which patents are hereby incorporated by reference. The invention is therefore described below for use in cleaning such disc-type filters, but it will be appreciated that the invention could also be used for cleaning other types of filters, and also for producing high-pressure compressible fluid pulses for other applications.
Many filters generally, and disc-type filters in particular, may be cleaned by back-flushing, i.e., by introducing a pressurized fluid through the filter outlet to back-flush the filter body through the filter inlet. When the filter is used for filtering air and includes electrodes for producing an electrostatic field to enhance the filtering action as described in U.S. Pat. No. 5,797,978, the electrical connections to the electrodes may also be reversed so that the electrostatic field will repel the dirt particles from the surfaces of the filter body and thereby enhance the back-flushing of the filter body.
U.S. Pat. Nos. 4,364,751 and 4,504,293, describe other techniques for cleaning air filters, utilizing a system of tubes, valves and nozzles which generate pulses of clean air jets directed through the filter in a direction opposed to the normal air flow path. The tubes restrict the air flow so that the jets must be released successively in a time sharing cycle. Such pulse jet cleaning devices, are therefore not effective in thoroughly cleaning the filter body, and moreover are relatively expensive to produce and to maintain.
An object of the present invention is to provide a novel filter-cleaning device which is capable of thoroughly and efficiently cleaning filters, particularly the air-type disc filters, but also other types of compressible fluid filters. Another object of the invention is to provide a method of cleaning filters; and a still further object of the invention is to provide a novel compressible fluid pulse generator particularly useful in cleaning the filters, but capable of use in other applications.
According to one aspect of the present invention, there is provided a filter-cleaning device for cleaning a filter having a filter body, a filter inlet for fluid to be filtered, and a filter outlet for the filtered fluid, the filter-cleaning device comprising: a compressible fluid pulse generator including a pressure tank, a tank inlet for inletting a compressible fluid, a tank outlet for outletting the compressed fluid, and a valve member normally in a closed position closing the tank outlet, but being actuatable to quickly move an open position to produce a high-pressure compressible fluid pulse at the tank outlet; the tank outlet being connectable to the filter outlet such that actuating the valve member applies a high-pressure high-flow impulse of the compressible fluid to the filter outlet to back-flush simultaneously the complete filter body by the high-pressure high-flow compressed fluid impulse.
According to further features in the preferred embodiment of the invention described below, the valve member is in the form of a piston movable within a cylinder in the tank; the cylinder having a closed end, and an open end aligned with the tank outlet; the piston being normally urged to its closed position to close the tank outlet by the fluid pressure within the cylinder between its closed end and the piston, and being actuatable in a fast-action manner to quickly move to its open position by the release of the pressure between the piston and the closed end of the cylinder.
According to still further features, the cylinder is formed with a large passageway therethrough adjacent its open end for directing the pressurized fluid within the tank to the tank outlet in the open position of the valve member and thereby for producing the high-pressure fluid pulse at the tank outlet. In addition, the inner diameter of the cylinder is reduced at the open end thereof aligned with the tank outlet to define an inner annular shoulder in the cylinder; and the outer diameter of the piston is correspondingly reduced at the end thereof facing the tank outlet to define: an outer annular shoulder engageable with the inner annular shoulder of the cylinder in the closed position of the piston, a large diameter section on the side of the shoulder facing the closed end of the cylinder, and a smaller diameter section on the side of the shoulder facing the open end of the cylinder The piston includes a first sealing ring on the large diameter section, and a second sealing ring on the smaller diameter section, which sealing rings are such that in the closed position of the piston, they are on opposite sides of the large passageway adjacent the open end of the cylinder.
As will be described more particularly below, such a cleaning device is particularly effective for cleaning air filters, since it produces a very quick-action opening of the valve member, and thereby produces a high-pressure high-flow impulse having a sharp front propagating in a velocity close to the speed of sound to the filter outlet which is effective to simultaneously flush all the filtering passageways of the filter. Such a cleaning device is particularly useful for producing an air blast for back-flushing air filters of the disc-type, but can be used also for back-flushing other types of filters for air or other compressible fluids, such as of the fiber type.
According to another aspect of the present invention, there is provided a compressible fluid pulse generator particularly useful for cleaning filters by back-blow flushing, but also useful for other applications requiring the generation of high-pressure fluid pulses. The invention also provides a method of cleaning filters by back-blow flushing using the novel compressible fluid pulse generator.
Further features and advantages of the invention will be apparent from the description below.